Here's a place where I can post my thoughts on new papers, provide updates on my projects, and post info that will eventually be on my website The Theropod Database - http://theropoddatabase.com/ . It will center on theropods, but may delve into other topics as well such as phylogenetics.

Saturday, August 6, 2011

Pneumatic disappointment

Benson et al. have a new paper out on theropod postcranial pneumaticity which I was extremely excited about, but the paper itself came as quite the disappointment. Not the general conclusions, which I agree with, but the data collection. The abstract reads "We review recent work on the significance of pneumaticity for understanding the biology of extinct ornithodirans, and present detailed new data on the proportion of the skeleton that was pneumatised in 131 non-avian theropods and Archaeopteryx." With supposed pneumatic ilia in Piatnitzkysaurus and others, Buitreraptor's pneumatic furcula, Shixinggia's pneumatic femur and other recent records, examining 131 theropods for postcranial pneumaticity would be quite enlightening. It's one of those features that is easily missed unless looked for, not often described, and rarely apparent in photos or illustrations. This is especially true for coelurosaurs, since most of the reported unusual pneumatic bones have been from them. All of the authors (Benson, Butler, Carrano and O'Connor) have done excellent detailed work before, so my expectations were high.

The meat of the paper is appendix S1, which contains all of the primary data. It's available here for those who are interested. The first problem is that it's all axial, so there goes my hope of getting some real info on how common appendicular pneumaticity is. More disappointing though is that only 12 of the 99 coelurosaurs are coded from seeing real specimens. The rest is all from the literature. Not that I'm one to frown on using literature, since that's where much of my data comes from too. And Benson et al. are usually good at determining which data can be coded from the literature and noting when information is from a figure, data matrix, etc.. But the information is basically what I could (and have) accumulated myself, with a few new additions thanks to personal communications with Balanoff and Brusatte, but then again I have my own sets of unpublished photos and AMNH observations with data not used by Benson et al.. I suppose I should be happy since this backs up my thesis that papers covering many taxa usually rely mostly on the literature and that my own upcoming paper explicitly describing codings in coelurosaurs is comparable in this measure to one written by four professional leaders in the field. But this time I was hoping for something more, akin to what Nesbitt et al. (2009) did for theropod furculae.

3 comments:

The paper does preface itself with "postcranial axial skeleton." Now, arguably, much of that essential survey on the vertebrae has been conducted by a variety of authors that immediate direct referral in THIS study was limited. Certainly, however, a limb-based review would warrant much more immediate attention and require each of the specimens mentioned to be examined personally. With authors like Steve Brusatte and Roger Benson, I don't think this is a problem. And while Matt Wedel is focused primarily on sauropod[omorphan]s, I'm fairly certain virtually all of the significant specimens he's discussed were examined personally (I'd have to check, and correct me if I'm wrong).

Appendicular and accessory skeletal evidence for pneumaticity is a project in and of itself more extensive than axial work, and it would have to be tackled initially (I think) from assessing the form of appendicular diverticula in birds, which is not exactly as well studied as axial and soft-tissue diverticular invasion.

To see and code all 99 included coelurosaurs directly in the way you suggest would take a vast amount of time and financial support. Although all of the authors are very interested in the evolution of pneumaticity (and three have very substantial theropod experience), none of us are dedicated coelurosaur specialists. It was never the intention of this paper to generate vast amounts of completely new anatomical data on pneumaticity in coelurosaurs – that was beyond our time constraints. Instead we attempted for the first time to summarise and synthesise all of the existing data, published by others or collected previously by ourselves, on the distribution of postcranial pneumaticity in order to draw out broad scale patterns and trends, as well as test quantitatively for the first time for non-avian taxa the relationship between phylogenetic position, body size, and pneumaticity. It also seems a bit odd for us to be criticised for synthesising data from the literature, given that, as you mention, this blog has often argued against the necessity of seeing material first hand... So you could have synthesised this data yourself - fine, but no-one had actually done that previously, at least not since Britt in 1993.

We focused on axial pneumaticity for very explicit reasons discussed in the text – appendicular pneumaticity is too rare in non-avian theropods to analyse in a statistically meaningful manner. This study represents a step forward because we quantitatively synthesise data from a very large number of species in order to draw broad macroevolutionary conclusions, rather than focusing qualitatively on one or a few exemplar taxa.

I am very proud of my involvement in this paper – I think it is among the most important I have contributed to – and I’m pretty sure my co-authors feel the same way. I think you've really missed the point as to what this paper was all about.

Thanks for the comment, Richard. I agree with all of your points, and in all fairness should have pointed out that the non-coelurosaurs were much better represented by examined specimens (43 of 64). It is a good paper. The data's basically all correct and good judgements were made when not to trust the literature (e.g. ornithomimosaurs). It's just not my dream paper the abstract got me excited for.